Radon is a natural radioactive noble gas. It is generated by the decay of radium. There are thirty nine known isotopes of radon from 193Rn to 231Rn.The most stable isotope is 222Rn (hereafter radon) with a half-life of 3.823 days. Four isotopes, 222Rn, 220Rn, 219Rn and 218Rn occur in trace quantities in nature as decay products of, respectively.
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